This invention relates to the purification and reclamation of oils of various types. It is particularly concerned with the removal of water from oils.
It is generally agreed that oil nevers wears out mechanically. The lubricating quality of oil is inherent in the oil, and truly clean oil can be used indefinitely. As long as dilution by liquid contaminants (such as water and acids), gaseous contaminants (such as air) and particulate contaminants (such as dirt, metals, bacteria and other suspended solids) is prevented, the original properties of the oil are maintained. Oil degradation is generally caused by oil containing any one, or a combination, of the above contaminants. Of these contaminants, one of the hardest to eliminate is water since particulate contaminants are generally satisfactorily removed by filtration methods whereas water is not.
Water exists in oil in two phases, as water in solution with the oil (dissolved oil) and as free water which is either separated from the oil or emulsified with the oil. The presence of water in solution in an oil is undetectable by visual means, since it is not present in the form of droplets. Free water present in an oil exists as droplets suspended in the oil. These droplets are often so fine and so well dispersed that, on casual observation, the oil appears to be clear. However, above certain levels, the oil is no longer clear, and the presence of water in these quantities is easily detected by visually observing its cloudy, muddy appearance. The state of dispersion of free water in oil varies dependent upon the additives present in the oil. High grade lubricating and hydraulic oils contain anti-corrosion and anti-wear additives which tend to maintain the water as a stable dispersion, of very fine droplets.
The presence of this water in oil renders the oil unsatisfactory for use because free water present in oil often tends to collect in low spots and dead spots in equipment and causes serious corrosion problems. In addition, water in oil is conducive to oil breakdown by chemical oxidation, with consequent acid formation. Oil with the absence of water, even when exposed under oxidizing conditions at high temperature, shows a substantially reduced tendency to form organic acids which can be extremely corrosive. Further, water in oil can promote the polymerization of oil to form larger long chain molecules, which in turn cause viscosity change and generation of solids (gums, tars, etc.) harmful in terms of clogging orifices, and causing abrasive wear.
Many systems have been utilized in an attempt to purify and reclaim oil. These include centrifuges, coalescers, filtration units and vacuum distillers. However, none of these systems have been effective in providing a continuous process for removing both free and dissolved water and other impurities from oil in an efficient and economical manner.
For example, one system similar to that of the present invention is that disclosed in U.S. Pat. No. 3,561,193. That system, like the present invention, removes water from oil through a vacuum distillation procedure. However, the system disclosed in that patent is deficient in that the vacuum distiller is only capable of removing the water dissolved in the oil. It is not capable of removing the free water during the distillation process and thus the free water must be removed separately, through the use of filters before the oil even reaches the distiller. This makes the equipment more cumbersome and slows down the process in that one using this process must be sure that all the free water is removed before the oil reaches the distiller.
In addition, in the system disclosed in U.S. Pat. No. 3,561,193, the water which is removed from the oil in the distiller is removed from the system directly through the vacuum line and pump. This necessitates using a relatively large capacity vacuum pump and also presents the risk that the water will accumulate in and damage the vacuum pump.
It is therefore an object of the present invention to remove virtually all the water, both free and dissolved, from oil during the distillation procedure without the need of extra filter elements to remove the free water.
It is a further object of the present invention to remove virtually all the water, both free and dissolved, from oil through the use of a considerably smaller capacity vacuum pump and with a minimum danger of damage to said pump than has been heretofore possible.